1. Field of the Invention
This invention relates to a light emitting element and a method of manufacturing the same.
2. Related Background Art
Various kinds of light emitting elements have heretofore been utilized in various kinds of optical apparatuses; for example, in a printer apparatus or the like for forming images by an electrophotographic method, a semiconductor laser is utilized as a light emitting element for exposure. The semiconductor laser is generally formed in a thin film laminated structure, and a laser beam is induced and emitted in a lengthwise direction from a rectangular parallelepipedic laser resonator (stripe).
Such a semiconductor laser will hereinafter be described as an example of the light emitting element according to the prior art with reference to FIGS. 1 and 2 of the accompanying drawings. FIG. 1 is a typical perspective view showing the appearances of the semiconductor laser, and FIG. 2 is a longitudinal cross-sectional view taken along the line 2--2 of FIG. 1. Herein, longitudinal, left to right and vertical directions will be referred to with reference to FIG. 1, but these are conveniently used to simplify the description.
The semiconductor laser 1 exemplified as a light emitting element is provided with a laser resonator (stripe) 2 as a rectangular parallelepipedic light emitting portion elongated in a longitudinal direction (front-rear direction), as shown, and this laser resonator (stripe) 2 is enclosed in laser diode chip 3 which is a rectangular parallelepipedic enclosing portion flat in a vertical direction.
First and second electrode layers 6 and 7 are formed on a cathode surface 4 and an anode surface 5, respectively, which are the two vertically opposed surfaces of the laser diode chip 3, and the first electrode layer 6 is connected to a stem 8, and the second electrode layer 7 has a bonding wire 9 connected thereto.
The laser resonator (stripe) 2 comprises, for example, GaAs or the like, and when electric power is supplied thereto in a vertical direction, it induces and emits a laser beam in a longitudinal direction which is a lengthwise direction. The laser diode chip 3 comprises, for example, GaAlAs or the like, and has electrical conductivity and a light transmitting property, and satisfactorily transmits a light beam, and is capable of direct radiation for satisfactorily observing an electron beam.
The first and second electrode layers 6 and 7 are formed of a metal such as Au, and electric power for causing the laser resonator (stripe) 2 to emit light is supplied thereto through the laser diode chip 3. The bonding wire 9 and the stem 8 are formed of a metal such as Au and supply electric power for causing the laser resonator (stripe) 2 to emit light to the electrode layers 6 and 7.
The semiconductor laser 1 of such structure as described above actually is disposed in a cylindrical package (not shown) by the stem 8, and a driving circuit (not shown) is connected to the stem 8 and the bonding wire 9 through the connection terminal or the like of the package.
When in such a state, electric power is supplied from the driving circuit to the first and second electrode layers 6 and 7 of the semiconductor laser 1 through the bonding wire 9 and the stem 8, this electric power is supplied to the laser resonator (stripe) 2 through the laser diode chip 3 and thus, this laser resonator (stripe) 2 induces and emits a laser beam in the forward direction, i.e., in a lengthwise direction.
The semiconductor laser 1 as described above induces and emits a laser beam from the laser resonator (stripe) 2 by supplying electric power to the first and second electrode layers 6 and 7.
However, the semiconductor laser 1 as described above may suffer from the occurrence of the destruction or abnormality of the crystal in the laser resonator (stripe) 2 due to electrical stress such as static electricity or an external serge voltage. Also, if the time for which the semiconductor laser 1 is used is accumulated, the destruction or abnormality of the crystal may occur in the laser resonator (stripe) 2.
So, when the semiconductor laser 1 is to be developed as a product, it is important to observe the state of the destruction or abnormality of the crystal of the laser resonator (stripe) 2 as described above and clear up the cause thereof and take an effective countermeasure. In this case, it is useful to actually supply electric power to the electrode layers 6 and 7 of the semiconductor laser 1 to thereby cause the laser resonator (stripe) 2 to emit light, and observe the dynamic state thereof by an optical microscope or an electronic microscope.
In the prior art semiconductor laser 1, however, the laser diode chip 3 enclosing the laser resonator (stripe) 2 therein physically transmits a light beam well and is capable of direct radiation, but the electrode layers 6 and 7 formed on the upper and lower surfaces do not satisfactorily transmit a visible ray of light or an electron beam. Therefore, it is difficult to observe the laser resonator (stripe) 2 emitting light from the outside of the semiconductor laser 1.
If, for example, the upper electrode layer 7 is peeled off, it is possible to observe the laser resonator (stripe) 2 from the outside by an optical microscope or an electronic microscope, but when the electrode layer 7 is peeled off, electric power cannot be supplied to the semiconductor laser 1 and therefore, the laser resonator (stripe) 2 emitting light cannot be dynamically observed.
In FIGS. 1 and 2, both sides of the laser diode chip 3 are opened, but these both sides are actually extremely narrow in width as compared with the upper and lower surfaces. In addition, each layer is laminated in a vertical direction, and therefore, it is actually difficult to observe the laser resonator (stripe) 2 from the sides of the laser diode chip 3.